Alternating-current signaling system



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ca/crlcl EPrn f AT ORNEY Patented Apr. 2, 1929.

UNITED STATES PATENTgOFFlC-E."

FREDERICK EUGENE PERNOT, OF LONDON, ENGLAND.

ALTERNATING-CUBRENT SIGNALIH G SYSTEM.

Application filed November 6, 1924, Serial No. 748,080, and in Great Britain November 28, 1923.

This invention relates to improvements in alternating current signaling systems and has particular reference to those types of telegraph signaling systems wherein the signal elements are formed by trains or": alternations of an alternating current. The invention has for its principal object to secure a more rapid rate of signaling, as well as greater certainty and precision in the formation of the signals.

The invention is applicable to those systems wherein a single alternating current either per se or in combination with direct current is used for the transmission of a single series of messages, as well as to those systems wherein several alternating currents, either per se or in combination with direct current are used'tor the simultaneous transmission of a plurality of messages.

The principal feature of the present invention consists in the production, in alternating current signaling systems, of change of phase in the alternating current, or currents, used in the formation of the signal elements.

Another feature of the invention consists in the provision of means in alternating current signaling systems whereby in signaling a change of phase is secured for each successive signal. whereby a better definition is obtained in the formation of the signal elements and thereby a higher possible speed of signaling.

A further feature of the invention is found in the provision of means whereby the signals which are characterized by currents of different phase are caused to actuate'a receiving device in a manner dependent upon the phase of the alternating current comprising the signal. i

A still. further feature of the invention 40 consists in the provision of means whereby the received signals characterized by currents of different phase are caused to interact or co-act with locally produced periodic actions or force components in order to detect and/or interpret the changes of phase ofthe signal current.

Yet another feature of the invention is "found in the provision of means operating in connection with signals characterized by currents of different phase whereby synchronism is maintained between the A. C. transmitting and receiving apparatus.

Another feature of the invention consists in the utilization in an alternating current signaling system, of cable code signals, and in particular block cable code signals.

Subsidiary'features of the invention comprise a. The utilization of a mechanical, synchronously driven, rectifierfor the reception of alternating current signals;

6. The use of a receiving instrument having a synchronized alternating field for the purpose of receiving alternating current, cable code signals;

0. The provision of means for maintaining a constant frequency in the transmitted alternating signal current; and

(Z. The provision of means for driving an automatic transmitter in step with the alter nating current source used for signaling.

By expression change of phase andrby similar expressions is to be understood. alteration of the phase by any required amount, but in particular by 180 degrees this particular degree of change amounting to phase reversal.

Further features of the invention Will be apparent from the following description and accompanying figures, wherein:

Fig. 1, shows a system adapted to reverse the phase of successive alternating current Morse code signals by reversing the direction of alternator field current.

Fig. 2, depicts the types of A. C. signals produced by the arrangement of Figure 1.

Fig. 3, shows a system adapted to reverse the phase of successive Morse code signals by reversingthe output leads of an A. C. gen

crating source.

Fig. 4, shows a type of receiving system for the reception and regularization of reversedphase Morsc'code signals. i

Fig. 5, illustrates the manner of application of reversed-phase A. C. Morse code signaling for establishing a superimposed communicating system on a submarine cable normally operating with direct current.

Fig. 6, shows a method for producing reversed-phase A. C. cable code signals by operating on an alternator field.

Fig. 7, shows typesof A. C. cable code signals produced by the system of Figure 6, and the cfi'ect of rectifying such signals.

Fig. 8, is adapted to describe how, by the use of a commutator, suitable currents are produced for the purpose of establishing synchronism between receiving apparatus and the receivedalternating current.

. Fig. 9, shows a complete equipment adapted to receive alternating current cable code signals by means of a rectifying commutator.

Fig. 10, shows an alternative system for receiving A. C. cable code signals by means of alternating-field relays instead of rectifying commutator.

Fig. 11, depicts a method for producing A. C. cable code signals of very constantfrequency without the use of a rotating alterna-tor.

Fig. 12, shows a governor adapted to con trol the speed of a motor-driven alternator for the production of constant-frequency cable code or Morse code signals.

Fig. 13, shows a methed'for driving an automatic transmitter forming the signals in step with an alternator producing the signal current. I

Prefatorially, it may be remarked that British Patents Nos. 176,827, dated Oct. 11, 1920, 17 8,87 3, dated Oct. 29, 1920, and 203,045, dated May 31, 1922, describe various methods of utilizing-trains of alternating current as signal elements in the multiplex transmission of signals. The connnonsignaling code utilized in connection with such systems is the Morse code, wherein the signal elements consist of dots and dashes which are distinguished from each other by the difference in duration of the signal impulses comprised by thetrains of alternations. Spaces between signal elements commonly comprise a mere absence of alter-n ating current. In the operation of such systems it is commonly found thatthere is a tendency for the train of alternations to persist after the tern'iination of a signal element, and since spaces are supposed to consist of a mere absence of alternating current, it becomes necessary to make the spaces long enough actually to realize a condition of zero current. The possible speed of signaling is therefore reduced because of the tendency of the alternations to persist. The growth of a signal is not instantaneous, either as measured in terms of the current itself or in terms of the movement of a device used in the reception of the signals, and this condition adds to the difficulty brought about by the persistence of effects after the proper time for signal termination, as previously mentioned. 7 I

In accordance with the present invention it is proposed to transmit (in Morse dot and dash code) each successive signal element by alternating current reversed in phase to that used for the preceding signal element. The small alternations persisting after one signal element will then be neutralized by the small preliminary alternations of the following signal element, anda definite zero condition will therefore be secured at the instant when the two trains neutralize each other. The space between signal elements, can, therefore, be shortened, resulting in a higher rate of signal formation.

If at the receiving end the alternating current be rectified at the instants when the current passes through its zero values, the direction of the rectified current impulses will reverse when the phase of the alternating current fed to the rectifier reverses, and consequently the direct-ion of deflection of any ordinary type of galvanometer coil connected to the rectifier will reverse also. Deflection in one direction can be interpreted tomean a dot in a signaling code and deflection in the reverse direction to mean a dash, so that by these means, therefore, it becomes possible to operate the alternating current signaling system in a fashion analogous to the ordinary cable code. he considerable time involved in the production of long dashes is not required, and the speed of signaling is increased by from 20 to 30 per cent by this feature alone. Since, in cable code working, there is no necessity for spaces between signal elements, they need not e inserted at the sending end except for letter and word spaces. The cross over from one phase position representing dots, say, to theoppesit-e phase position representing dashes can be made di rectly without an interposed idle period, and the utilization of this method of blocl'c signaling results in. a still further incr ase in speed.

As previously pointed out, the application of the invention to Morse code working con sists in causing successive signal elements be constituted by current whose alternations are in opposite time-phase position to those of the preceding signal.

' The arrangement shown in Figure 1 is designed to accomplish this result. The method shown is based upon British Patent No. 202,7 8 1, dated June 15, 1922, Figures 5 and 6, but has incorporated in it a relay device for reversing successive signals. At 1 is the armature of an alternating current generator, terminating in leads 2 and 2 fromwhich currentis delivered to whatever transmission system'may be involved; Signals are produced by making and breaking the current in .the alternator field winding 3. A battery or source 7 provides direct current for ex citation of field 3, and intermediate the source 7 and field 3 is a reversing switch 6, which controls the direction of current through the field winding. Resistance 5 and condensers are provided for controlling the field current as dcscribed in British Patent No. 202,784, dated June 15, 1922. The initial formation of signals is atkey 10, which may be a hand key or automatic transmitter, and this key controls the magnet 12 connected to the battery. 11. On signaling, armature 13 is attracted by the magnet 12 against the restraining force of spring 15, and the armature carries with it the headl l which consists of insulating material. The downward motion of the head 14tallows lever 17 acting under the forceof spring 17 to make contact at 17 On making this contact, field 3 is energized by current flowing from battery 7 through the reversing switch 6, leads 20, 21, and 19. (It is to be noted that in the downward or signal position the head 14 breaks contact between 16 and 16'.) During the excitation of the field 3, alternating current signals are delivered from armature 1 by way of leads 2 to the system transmitting or utilizing them.

Upon opening key 10 at the termination of a signal the head 14 moves upward, first allowing contact to be made between 16 and 16, and then slightly later breaking the contact 17 and 17', thus interrupting the circuit between battery 7 and field 3. The current existing in field 3 persists because of the self inductance and dies away in the closed circuit through lead 19, contacts 16 and 16', lead 18 and resistance 9.

The winding 8 of a polarized relay controls the operation of reversing switch 6, and the winding 8 is connected in parallel with resistance 9 by leads 8 and 8". At the termination of a signal, when contact 1616' is es tablished, the relay winding 8 is thus en ergized by the decay current from field 3, and when thus energized the relay acts to move the reversing switch 6 into its opposite position. The connection between battery 7 and field 3 is thus reversed during an idle period following a signal, and since the succeeding signal will be in an opposite direction the switch 6 will be moved back into the original position when this signal terminates. Thus, the switch 6 operates after every signal by the field discharge current, so that each signal is represented by current through field 3 opposite in direction tothe current of the preceding signal. As is well known, re versal of field current in an alternator reverses the phase of the output, so the desired result is accomplished.

The advantage, previously mentioned, of using successive reversals of phase in Morse signals will be apparent from a consideration of Figure 2, which shows the results normally obtained with existing apparatus and results as obtained by using apparatus as described in Figure 1. In this figure the shaded blocks in curve A represent two dots in Morse code, being the E. M. F. impressed on the field system of an alternator as shown in Figure 1 by the operation of contacts 1616 and 17-17 when no reversal in direction is accomplished (that is, without making use of the present invention). The dots occur between times 0 and t and t and t with a space between t and F. The field current grows and dies away slowly, so that between the instants t and t it does not have time to vanish completely before a new growth is started by the beginning of a second dot at time F.

Curve B shows the corresponding ouput E. M. F. of the alternator and it is seen that the E. M. F. still persists at time t when growth consequent upon the second dot begins. The minimum cyclic value ofE. M. F. incurve B occurs at time 25?. but even there the E. M. F. by no means vanishes, so that the two trains of alterations which shouldconstitute separate dots are scarcely distinguished separately; they merge one into the other.

Curve C shows the E. M. F. for two dots in Morse code as impressed on the field 3 of the alternator in Figure 1 by the arrangement there described. The dots are in opposite directions, as represented by the shaded areas, beingof the same duration and having the same spacing as in the case of curve A. Curve D of Figure 2 shows the resulting output E. M. F. of the alternator. From the beginning, 0 to t the output curve D is identical with curve B, but at t the second dot begins in a reverseddirection, so that the E. M. F. curve Dis forced to become zero before it builds up again to form the second dot.. This is to be observed at the time marked S where a definite space occurs between the twotrains of alternations constituting separate dots. v

The curve D, because of the definite space S represents a satisfactory working state of affairs, whereas the curve A, because of the lack of definition, does not. Tobe made workable, the time between dots in curve A would have to be prolonged in order to secure their separation, and therefore a slower signaling speed would result than in the case of curveD, which, as pointed out, is satisfactory.

The above analysis of the effect of successive'phase reversals has been based upon the production of alternating current trains by operation upon the field of an alternator, but the same description applies in the case of any kind of system transmitting or utilizing the alternating current trains, and wherein building up and dying away of the alternating current take place comparatively gradually. This is thecase in any type of resonant system, and the whole advantage of reversed phase signaling for Morse code working depends upon the bettering of the definition between signals as described.

An alternative type of apparatus for reversing the phase of successive signals is shown in Figure 3, and the type there described does not depend for its action upon the discharge current from an inductive cir cuit as the alternator field winding) as is the use in Figure 1. In Figure 3 the reversing switch is placed between the alternating current source and the output circuit so that phase reversals do not depend, as in Figure 1, upon the reversal of field excitation. In

Figure 3, 23 is the alternating current source 1 iii posite sense consequent upon signals formed at the transmitter or key or the like, 31. At

28 is a reversing switch operated by a polarized relay whose winding is 29. A battery 80 operates through this reversing switch and the key 31 to effect the motion of either one of the two polarized relays 22 and 25. Those two latter relays are oppositely polarized so that one or the other operates depending upon the direction of current in their two series-connected winding 22 and A bias, as by springs 22 and 25" is imposed on the arinatures of the respective relays so that contact is normally maintained against the upper contacts 22 and 25", thus shortcircuiting leads 24 when no signal is passing. The winding 29 of the reversing switch (relay) is connected through leads 32 and 34, and condenser 26 and resistance 27, acrossthe main relay windings 22 and 25, the latter being connected by way of lead 33 through the reversing switch and battery to key 31..

Beginning with the reversing switch 28 in its upper position, a closure of key 31 sends current from battery upwards through windings 25 and 22, thus deflecting, say, the upper arniature 22 to make contact at 22. This connects source 23 to leads 24 in one direction. The condenser 26 has meanwhile become charged (its charging current confirming the previously existing upward position of switch 28) to the potential of battcry 30. Upon releasing the key the discharge current from condenser 26 flowing through coils 22 and 25 flows also through winding 29 and causes the reversing switch 28 to pass to its downward position. Armature 22 loses its deflection and the leads 24 are again short circuited at the termination of the signal. Everything is now as it was originally except that the switch 28 is reversed, so that the next signal will reverse the current in windings 22 and 25, causing armature 25 to deflect and thus produce a reversal of phase between the source 23 and the output leads 24. These actions take place repeatedly, causing successive signals to be sent out first through relay 22 and then through relay 25, establishing a reversal of phase in the alternating current supplied over loads 24 from alternator 23 for each signal, as desired. i

It has so far been shown how to produce the reversed-phase alternating current Morse code signals, and it remains to describe meth ods for effectually receiving them. One method for doing this is described'in British Patent No. 218,361 dated Mar. 27, 1923, for in the method there described the act of reception is dependent upon the heating efztect of the received alternating current signal; and this is independent of whether the phase of successive signals is reversed or not.

Another method for receiving the reversed-phase Morse code signals is shown in Figure 4. In this figure, the arriving alternating current signals enter-at leads 85 and pass into the coil 36 of an ordinary fork relay. The coil 36 carries a light air-damping vane 36 and is supported between the poles N and S of a magnet by the usual stretched wire or fiber suspension 87, 38 and bridge piece 39. The coil 36 carries also the two antennae 40 of gold wire or the like which are electrically joined together and which play between the two metal butts 41, the butts also being electrically joined together, but mounted far enough apart so that the antennae 40 do not touch them when the coil 36 is stationary. An arriving alternating current signal causes the coil 86' to vibrate and the antennre 40 to make contact successively against the two butt-s 41, thus repeatedly establishing connection between leads 42 and 43 joined to the antennre and butts, respectively. A battery 46 acts through the butt-antennae contact by way of leads 42 and 43 to operate a more powerful relay whose main winding is shown at 47. A condenser 44 in series with a resistance 45 connected between leads 42 and 43 serves to minimize the eiiects of the small interruptions to the circuit between but-ts and antennae when the latter are vibrating under the action of an arriving alternating current signal. Substantially steady current from battery 46 is thus maintained through relay winding 47 as long as the train of alternations constituting a signal lasts.

The relay winding 47 may be that of any ordinary relay suitable for the operation of any subsequent receiving device of usual type, such as a siphon recorder as shown, comprising coil 56, siphon 57 attached thereto, and paper slip 58, the recorder being actuated by current from battery 51 through contact and relay tongue 50. It is preferred, in this connection, to employ a modified form of relay to operate contacts 50 and 50, because the signals established by the antennae 40 and butt 41 cont-acts consequent upon the passage through coil 36 of alternating current signals similar to those shown by curve D of Figure 2, may be of somewhat irregular duration, so that it becomes desirable to provide means for making the final signals, as recorded, more regular. The relay tongue 50 is held by a magnetic bias, or by a spring 49,normally against the upper contact 50", but the action of signal current through the main winding 47 causes ton gue 50 to make contact against 50', thus sending a signal to the recorder 56. In addition to the main winding 47 there is provided an auxiliary winding 48 in the relay. Auxiliary winding 48 is connected through resistance 52 and condenser 53 across contacts 50 and 50", as shown. Lead 51 connects one side of battery 51 to the tongue 50. The

"ainst contact 50", a

auxiliary coil 48, and connections to the auxiliary coil are made that this condenser current on discharging tends to establish the tongue contact at 50 still more firmly, so that even though the signal current through the main winding vanished, the auxiliary coil would still maintain the contact until the charging current into condenser 53 became so small'as to release tongue 50 against the action of the bias i9. By suitably adjusting resistance 52 and condenser (as well as resistance the instrument can be made to produce a minimum length of signal, thus ensuring that no dot becomes so short as to be ine'ective in operating the recorder 56. Vhen tongue 50 moves back against stop 50 at the end of a signal, the discharge of condenser 53 through the auxiliary winding 48 maintains that contact until the discharge current becomes small, and therefore the arrangement as described operates to ensure that no space shall be less than some minimum length of time. The action as above described is extremely useful in practice, offecting a marked improvement over signals as would be received without its aid from a receiving relay of the vibrating-coil type, 36, 40 and 41. In adjusting the resistance 52 and condenser 53 of the auxiliary winding 48, care must be exercised that the sum of the compulsory minimum marking and spacing times does not exceed the total time period of the elementary received signals; otherwise failure to'reproduce the signals results. The relay contacts 50, 50 and 50" are shown as operating a recorder 56, but they may be used for any of the usual purposes well known in. the art, for example, in place of recorder coil 56 and inductance 54 there may be substituted the two magnet windings of the usual perforating apparatus, used for recording the signals in the form of perforated paper taps, etc.

The methods of reversed-phase alternating current signaling herein described are particularly advantageous in telegraphy over submarine cables where, because of the transmission properties of. the cable, it is usually necessary to work the alternating current system at a low frequency. As a consequence of the low frequency a rapid rate of signal formation can only be secured by limiting the number of alternations or cycles per signal element to a minimum; and this in turn necessitates the use of devices as herein do scribed. Further, the alternating current signaling system is of value in submarine cable telegraphy pi'ineipally when it is used as a channel, or c annels, of communication superimposed upon the usual or ordinary direct current working of the cable.

Figure 5 illustrates two cable stations adapted to operate for communication be tween them with reversed-phase Morse code signals, while one of the stations is equipped also with usual direct current apparatus for communicating with a third station also connected to the same cable. In Figure 5, 1, 1, and 1" represent the cable joining three stil tions, X, Y, and Z; Zbeing a remote station not shown in the figure. Stations X and are equipped with A. C. (alternating current) apparatus as described for communicating with each other, and station X is also equipped with D. C. (direct current) apparatus for communicating with station Z. Both sets of communications, Z.X and XY can be carried on in both directions (duplex) and simultaneously. The essential features of the systems shown in Figure 5 have been described in British Patent No. 203,045 dated May 31, 1922, so that they need only be briefly mentioned here. At station X where both A. C. and D. C. sending and re ceiving apparatus are provided, there are: 2', the cable; I), the duplex bridge with apex at a; transient moderator, or hlter circuits, 0, c, and c for the pnr ose and as described vin British Patent No. 2 3,045 dated May 31,

1922; (Z, the armature of a direct current gerrorator for producing D. C. signals as ie. scribed in British Patent No. 202,784 dated June 15, 1922; and e, the armature of an alternator with its field winding e arranged for the production of reversed-phase A. C. Sig nals as described in connection with" F "re 1 hereof. The two sources (1 and e wor in series as described in British Patent No. 202,- 7 84 dated June 15, 1922. For receiving there is provided the usual D. C. receiving appanh tus g, connected across the duplex bridge, and there is also provided the artificial line The A. C. receiving apparatus is connected to the duplex bridge through a condenser k, including auxiliary balancing means It and It as described in. British Patents Nos. 201,- 603 dated Apr. 8, 1922 and 203,045 dated May 31, 1.922. Tuned circuit Z has magnetic coupling m with tuned circuit n,- the latter connecting through a condenser o to amplifiers p and p. A relay system 1' as described in connection with Figure 4' hereof is connected to amplifier p through transformer g. The relay system 1' ma be mod to operate any desired further as described under Figure 4. Station X is thus equipped to send and receive D. C. signals,

and simultaneously therewith to send and receive reversed-phase Morse code alternating current signals.

. Station Y is joined to the cable 71 and 2' through a condenser S. This station is equipped to utilize only A. C. signals for simulate the cables 2" and duplex communication .with station Z. At A is the apex of a duplex bridge B, and to balance the bridge, condenser S simulates condenser S,*and artificial lines J and J 2' extending in either direction from station Y. The A. C. transmitting system connected to apex A is similar to that of station X, containing transient moderator C, G and C, with an alternator E and its field E arranged to produce reversed-phase alternating current signals as described in Figure 1 hereof. The

Y A.C. receiving system is identical I vith that of station .X, comprising condenser K in. the

connection to the duplex bridge, tuned circuit L, magnetic coupling N to tuned circuit N, condenser O, amplifiers P and P, and transformer Q between the last amplifier and the receiving device R. In this case a form of receiver R is shown which consists of the ordinary siphon recorder, the coil of which carries the alternating current signals. .It records on the usual paper tape T the trains of alternations oi the type shown in curve D of Figure 2, which are thus made available for visual interpretation. Station Z at the remote end of the cable 71 is provided with the ordinary duplex D. G. equipment for communicz ting with station X. The toregoing description of the system shown in Figure 5 is included here to illustrate a type of practical application of the reversed-phase alternating current signaling method, and this completes the description of tiie methods employed in adapting the invention to ,Morse code Working.

and interpreting a. reversal of phase in the alternating current constituting the signal elements. The advantages to be gained by this method of signaling arise partly from the fact that cable code is a shorter Code than Morse code, and partly from other considerations to be described later.

Figure 6 shows an electric generator 61 having its field 62 connected to the control circuit comprisingcondenser 63 and resistancesfi i and 65, and further connected to the conventional type of cable code transmitting key 66, 66, and 66", and a battery or source 57. The arrangement is identical with that described in Figure 3 of British Patent No. 202,7 84, dated June 15, 1922, except that in this case the armature 61 is that of an alternating current generator. 68 and 68 are the output terminals by which the signals are delivered to the system transmitting and utilizing them. The action of the system shown in Figure 6 will be described in connection with Figure 7, which shows the types of signals produced. Curve A in Figure 7 represents the field excitation of the alternator in Figure 6, and comprises dot a space a dot a space a, and a dash a the dash being represented by field current negative, whilst the dots are represented by positive field current. Curve B represents in full line the E. M. F. output of the alternator at terminals 68 and 68. If the dot key were depressed over the full time represented in the curves, a steady alternating E. M. F. represented by the full line 0 dotted line 5 full line 6 dotted line Zffland dotted line Z), would be produced. l/Vhen the keys are n'ianipulated in accordance with curve A, the "full line of curve B is produced, causingalternating E. M. F. at b to represent a dot, a zero output as a. space at Z2 an alternating l M. F. output of unchanged phase for another dot at 6 zero for a space at I), and finally an alternating E. M. F. output of reversed phase as shown by the full line 7) representing a dash. The dots and dashes are distinguished, therefore, by a reversal of phase.

In cable telegraphy it is common practice to use block signals in cable code working. That is, a succession of signals of one sign (as dots) are run together into one long period of positive current, the number of dots contained therein being determined by the duration oil the prolonged signal. Similarly it is with sashes, and useless spaces are there by eliminated. In Figure 7, curve C shows how curve A may be shortened by using block signals. The dot, dot, dash oi curve A a e placed in immediate juxtaposition, becoming 0 c and 0, and the time required for the complete signal is shortened in the ratio of T the unit signal time in curve C, to T, the unit signal time in curve A. When the alternator field is excited in accordance with curve C then its output E. M. F. is shown by curve D, the two dots (Z and (Z appearing as a continuous train of alternations, but the dash Z) appearing in full line as an alternating E. M. F. reversed in phase from the dot This is indicated by the dotted line (Z which shows the E. M. F. which would be produced it (Z were a dot instead of a dash.

The visual interpretation of signals recorded in the form of curve D would be practically impossible, but if the alternating current signals D be passed through a commutator or reversing switch operating synchronously with the alternator, and reversing the signal current at the zero ii tant in every half cycle, the current delivered b the commutator will appear as in curve It. The dots c and 0 appear as a train of positive impulses, and the dash e as a train of negative impulses, and when this commutated current is passed through a relay or any usual type of recording instrument having a little inertia to carry it over the short gaps between the impulses, a record will be obtained from the current oi curve E similar to curve C, which is the ordinary type of" block signal in common use.

The solution of the problem or" cable code alternating current signaling thus consists in the provision of means. as shown in Figure 6, for forming the reve d-phase cable code signals and in the prov]. on of means, such as a synchronous comuuitator, to." interpreting the cable code A. C. t the type shown in curve D of Figure 7. Since the transmitter is at one end of the cable and the receiving apparatus at the other end of the cable, it is necessary, when the cable code A. C. signals are received through the medium of a reversing commutator, to provide means for keeping the receiving commutator running synchronously with the arriving alternating current, so that a result typified by curve E in Figure 7 may be secured. It the alternating current comprising a signal be purely sinusoidal and be comn'iutatcd at the instants of peak value, the current 'delivered by the commutator will have an avcrage value of zero, and hence will'not deflect an ordinary type of moving coil galvanometcr or a relay. In Figure 8, curve A shows alternating current signals, a dot at a and a dash at (1 reversed in. phase from a. Curve B shows the current (or E. M. F.) derived from A by commutating curve A at the times 17 1 9 etc. corresponding to the peak values. The average value of the curve B is seen to bezero, as mentioned, both for the dot Z) and for the dash b Curve C shows the result of commutating curve A at times (1 9 etc. delayed by an angle 6 behind the times 2), 12 etc. oi? peak values. The resulting commutated dot current 0 has a positive average value represented by the dotted line a. This average value c is consequent upon the delay 0 in the action of the commutator, and by passing the current through a relay, actions can thus be brought into play to hasten the commutator action and cause its reversals again to take place at the pealre instants of curve A. Conversely, if the times g 9 etc, of commutation occur ahead of the peak instants, the average current 0 would be negaeffect of a delay 0 in the instant of commutation produces a negative average current 0" during a dash a, whilst it produces a positive average current 0' during a dot a. If the action of this commutator (hereinafter termed the synchronizing conunutator) through a relay is to determine the direction of phase correction (to remove the delay 6) by the direction of the average currents c.

and c", it is obvious that either, one of the currents 0 corresponding to a dot, or 0" corresponding to a dash, .must be eliminated so as not to affect the subsequent relay and thus destroy the synchronizing action established by the other; or else both currents must be made to affect the subsequent relay in the same way consequent upon the phase error 0. This latter is readily accomplished by inter-posing a switch between the relay which utilizes the current from the synchronizing commutator for the purpose of phase corrcction and the synchronizing commutator itself. This switch is operated by the signals (of the type shown in curve E of F igure 7) themselves in such a way as to send the synchronizing current-s 0' and 0 of curve C, F igure 8, through either one of a double winding provided in the synchronizing relay, the direction of connection of these windings being made so that both currents c and 0 produce similar effects consequent upon the. delay 0 in commutator action.

Figure 9 shows diagrammatically a complete receiving system for cable code, alternating current signals. The system shown is based upon the use of two commutators, one commutating the received current at the zero times as shown in Figure 7 for the formation of rectified signals, and the other commutator commutating thecurrent at, or about, the peak value as shown in Figure 8 for the purpose of actuating apparatus to be described for maintaining synchronism between the commutator actions and the received alternating current. The two commutators will hereinafter be referred to as the signal commutator and the synchronizing commutator respectively. In Figure 9, at 9 are the leads coming from the transmission system, over which arrive the cable code alternating current signals to be received. At 71 is the signal commutator, and at 73 is the synchronizing commutator, both mounted on the same shaft 76, and so adjusted as to operate at times one-fourth of a cycle apart. Brushes and 70 conduct the signal current to commutator 71, and brushes 7e, and

corder is of the usual type and serves to writev the signals on a paper tape 79. An inductance 80 in series with the recorder serves to suppress the pulsations existing in the rectified signal current. A further impedance 81 or any other combination of resistance, inductance, capacity, etc. as is well known in the art may beused to shape the received signals. The tape record 79 is the final form in which the signals are received, but it is readily seen that in place of recorder 78 any usual type of relay may be used for sending the signals out over another circuit, or to operate an automatic perforator, etc, such devices being well known in the art.

The synchronizing connnutator 7 3 takes a portion of the received signal current and delivers it, after commutation, through brushes and 7 5 and leads 88 and 88 to further apparatus whose function is to keep the shaft 76 and the two commutators running synchronously with the alternating cur rent received. A relay 91 relay carrying two windings 89 and 89 (the windings having resistance shunts 90 and 90 as may be required) is supplied with the commutated current over leads '88 and 88, but between the relay 91 and the synchronizing commutator 73 is interposed another relay 82 whose purpose is to ensure that the commutated current corresponding to dots is delivered to one winding, say 89, of relay 91, while the commutated current corresponding to dashes is delivered to winding 89. This is for the reasons set forth in the description of Figure 8. Relay 82, with its series inductance 86 and shaping circuit 87 is similar to, and con-, nected in parallel with, the recorder 7 8, but instead of carrying a siphon it carries the antennae 83 of gold wire or the like which play between the metal butts 84; and 84. a When dots are received, contact is made by antennae 83 with butts 84, and when dashes are received contact is made with butt Sat. Thus, by way of butts 8e and 84: and loads 85 and 85 the current from the synchronizing commutator delivered byway of lead 88 to the antennae 83 is caused to pass through relay coil 89 or relay coil 89 depending on whether dots or dashes are being received over input leads 69. i

When the commutators 71 and 73 act in the wrong phase position with reference to the arriving alternating current, a current as typified by c in Figure 8 affects relay 91, causing antennae 93 to make contact with butt 94: when the commutator operates too late, and with butt 94: when it operates too early. The antennae 93 are very delicate and their contact with thebutts is unsuited to the control of large currents, so by means of battery 97, magnets 98 and 9S, and leads 95, 96 and 96 more powerful relay contacts 99 and 99 are actuated by relay 91. Dumping vane 92 is provided to relay 91, preferably moving in a viscous fluid to make the movement of relay 91 sluggish, as has been found best in practice. Finally, therefore, when contact 99 closes, it is because the act-ion of the commutators 7 3 and 71 is delayed, and when contact 99 closes it is because the commutators act too early, and these contacts are to be made to actuate mechanism designed to remove the phase errors in the commutator actions. The methods employed for doing this are similar to those described in British Patents Nos. 196,971 dated Jan. 4, 1922, and 213,302 dated Oct. 28, 1922, so that they need not be described here in great detail. 7

A vibrating reed 108' of any usual and suitable type, maintained in vibration by a battery 111 and magnet 110, drives a phonic motor 107 through leads 112, contacts 109, and battery 111. The phonic motor 1.07, through gearing 106 and 105, and shaft 103, carrying a damping (such as a mercury- .tilled) fly wheel 10 i, drives adiiferential gear 100, and through it the shaft 76 carrying the two commutators 71 and 7 3, which are thus driven at a steady speed. The frame 101 carrying the idler pinions of the differential gearing 100 has mounted on it a worm wheel 102; the whole is rotatable and controlled by the worm 114 driven (through gears if necessary, but not shown) by the armature 113 of a direct current motor whose field 115 is continuously excited by source 116. The motor 113 is connected by leads 117 to the two relay tongues 120 and 120' arranged with battery 121 and resistance 122 to act in the manner of a common cable code hand key to send. current over leads 117 to motor 113 in either direction depending upon which of keys 120 or 120 is actuated by its controlling magnet 119 and 119. Magnets 119 and 119 are energized by battery 118 act ing through relay contacts 99 and 99 respectively, and leads 123. Therefore, when relay contact 99 closes because of a late commutator action (as previously described), magnet 119 is energized, tongue 120 is de flccted, and current from source 121 is sent through the armature 113 in one particular direction. This causes the armature to 1'0- tate, and with it the worm 11%, which in turn rotates the worm wheel 102 and frame 101, thus advancing the phase of shaft 76 and the COHlllllltiLllOlS so as to remove the previously existing phase error. lVhen the commutators reach their proper phase position the deflections of relays 91, 99, and 120 cease,

and motor 113 stops running. Similarly, the motor 113 is driven in the opposite direction when relay 99 closes consequent upon an early action of the commutators. At the completion of each correction the motor 113 is brought quickly to rest by the short circuit to its armature through leads 117 and contacts 120 and 120, because the field 115 remains fully excited.

The above completes the description of the necessary synchronizing and receiving functions, but in order to minimize the number of phase corrections required a control is provided to the vibrating reed 108 driving the phonic motor 107 so as to eliminate those speed errors which cause deviations in phase (of the commutator action) to accumulate. Extending beyond the end of the vibrating reed 108 is a weak spring 124 constrained at some point along its length by the two stops 125 mounted in a sliding block 126. The sliding block 126 is moved backwards or forwards by the screw 127 operated by the toothed wheel 128 under the action of one or the other of pawls 129 or 129'. Pawls 129 and 129 are operated respectively by magnets 130 and 130, which in turn are energized by battery 118 through relay contacts 99 and 99' respectively and leads 131. IVhen contact 99 closes because of a retarded commutator action, magnet 130 is energized and pawl 129 moves down, turning wheel 128 and screw 127 in such a way as to move the butts nearer to the reed and thus increase the rate of vibration of the latter. This action takes place in addition to the phase correction through motor 113 previously described, and tends to eliminate the speed error which caused the phase error to accumulate. Opposite action through contact 99 and pawl 129 takes place when the commutator advances in phase because of the reed vibrating too rapidly.

Additionally the usual manual adjustment of the reed is also preferably provided, this adjustment being of particular advantage when setting the apparatus in operation since any unduly appreciable lack of synchronism can by these means be roughly eliminated when the apparatus will automatically make the further requisite fine adjustment in the manner described. In this manner synchronism is more quickly established than would otherwise be possible.

There are, of course, numerous modified forms for the apparatus described. The reed correction might be done as described in British Patent No. 213,302 dated Oct. 28, 1922, by gearing screw 127 directly to worm 114. In place of the small spring 124 a small weight might be arranged to slide along the reed. In place of starting and stopping the motor 113 for phase corrections, a reversing clutch might be used in connection with a steadily rotating shaft. In place of commu- 'tators of the commutator type as shown,

camor eccentric-operated switches might be used. In place of using two separate coils in relay 91, a single coil might be used with the direction of current through it controlled by relay 82. Various arrangements of well known types of relays can be utilized to perform the same, or analogous, functions as those shown. In practice, because of distortions in wave shape of the received alternating current, it is found to be advantageous to set the two comn'iut-ators 71 and 73 not exactly in quadrature, but at a slightly different angle. All such modifications are deemed to fall within the present invention, and are held to be useful modifications to be used as preference or circumstances may dictate.

Another method may be adopted for receiving the cable code A. C. signals. British Patent No. 205,843 dated May 25, 1922, describes a relay having an alternating field, through the action of which a one-way deflecting force is exerted on the relay coil carrying an alternating current signal. British Patent No. 196,971 dated Jan. 4, 1922, shows a method for maintaining the alternating excitation of such a relay in synchronism with the received current. By the provision of an intermediate relay to perform functions analogous to those of relay 82 in Figure 9, a system based upon British Patent No. 196,971 dated Jan. 4, 1922, and as shown in Figure 10 can be used for receiving cable code A. C. signals through the medium of an alternating-field relay instead of through the medium of a rectifying commutator and ordinary relay. In Figure 10, A. C. signals arrive over leads 132, are passed, if necessary, through a transformer 133, and thence over leads 134 and 134 to the relay winding 135 whose field 136 is excited by alternating current locally produced and kept in synchronism with the arriving signal current. This is the signal relay, its field excitation being maintained in phase with the arriving signal current. It deflects one way or the other for the dots and dashes in the arriving signals of the type shown in curve D Figure 7. Antennae 13. mounted on the coil 136 are normally in contact with both butts and constitute the apex of a Wheatstone bridge containing resistances 141, 141, 139, and 139 and battery 14.0. The said bridge is balanced and remains balanced until movement of coil 135 breaks contact between antennae and one of the butts. Current then flows through leads 1 12 and 143 forming the bridge crossarm, and through siphon recorder coil 151 and polarized relay coil 150. Dots and dashes break contact at butts 137 and 137' respectively, thus unbalancing the bridge 141, etc. in opposite directions, and causing siphon recorder 151 with its ink reservoir 145, siphon 151, and paper tape 152 to write thesignals. The relay coil 150 controls the motion of a reversing switch 15 i tln'oug'h the relay ton ue 153, so that the switch occupies one position when dots are received and the other when dashes are received. This receiving switch has a function analogous to that oi relay'82 in Figure 9, in that it serves to make similar the efiects of dots and dashes (their current) upon relay '156- which is used to maintain synchronisni between the alternatsource used for exciting the relay fields 136- and and the received alternating current.. Relay coil 156 is connected through leads 155 and 155 through reversing switch 154: to leads 134. and 13 i, and is thus in parallel with relay 13.5... Relay coil 156 carries antennae 15? adapted to make contact on deflection with butts 15.8 and 158, and thus througl'i leads 159 to actuate phase correcting: device 162 controlling alternator 163;, either as described in British Patent No. 1%,971 dated Jan. t, 1922, or by means of a differential gearin as described in Figure 9 hereoi, or in any similar or suitable manner, to; keep alternator 163' in synchronisin with the arriving signal current. Alternator 163 has its field 164. permanently excited; it is a two phase alternator, and by way of brushes or. terminals 14.61, 147, 1&8, and 14.93 and leads 165, 165, 166. and 166 excites the primary Winding 167 of an adjustable-phase trans tornrer. Relay winding 160 of the synchronizing relay is excited by way of leads ice-16.5 of the alternator, and relay held 136 of the signal relay is excited by way of leads 169 iii-our the secondary 168 of the! ad'- jxustable-phase transformer- Excitation of relay'fields 136,v and 160 should be substantially in quadrature, but the phase-adjusting transiornier 167-168 provides for changes from this condition it found desirable. action here would be analogous to adjusting the cominutators 1 and 73 of Figure 9 at a position dill'e-rent from rig-ht. angles, as reiierred to previously.

In Figure 10 the siphon recorder 151 might be replaced by a relay for operating" other kinds of well known receiving apparatus. Numerous other modification-s are possible Withinthe' principleof the present invention,

and such modifications are deemed to be inchided part of the: present invention.

A further method for operating the signal relay and the synchronizing relay is based upon the use of two. bolontieter bridges, polarized by locally produced alternating current, and thermally affected by the. received signals. This type of bridge is described by Irwin in British Patent No. 29,206 of 1910, and it is only necessary in this connection to utilize two oi such bridges, polarized by locally produced alternating currentes in phase quadrature with each other, and operating ordinary types of relays to supplant the relays'156 and 135 of Figure 10.

From the foregoing it is evident that the re The ception of reversedephase, cable code alternating current signals is dependent upon maintaining synchronisni between the: received signal current and some local operation at the receiving station. To do this it is essential that the received signals are C0111- prised of current of very steady, constant irequcncy. Figure 11 shows a method of producing A. C. cable code signals of very constant frequency. At 1.70: is a vibrating reed maintained in vibration by the circuit 171 in the usual way. Battery 1T3 is connected to the reed and by leads 173 to one side of each of twov coils 177 and 177". Contacts 172' and 172" on either side or" the reed connect to straps 17a and 174 respectively of a cable code The contact levers 175 and 175" of the key coimect'respectivcly to the other sic cs oi the two coils 177 and 177, throu h resistances 176 and 176 Condensers 110 and 178 are placed across the respective coils 1'77 and 177, and each coil has magnetic; coupling, 185 and 185" respectively to a coil 179;. but the coupling between. coils *7 and 1'77 themselves is negligible. Coil 179 included in a or "d circuit including coil 181 and con denser and resistance 180'- A liltit er'coil 183 having magnetic coupling. 182 with coil 181 has its terminals 18% and 184 connected to the system designed to transmit or utilize the signals. .Vhen key 1T5 is depressed, the alternate contacts at 172 and 172 supply inipulses to: coils: 177 and -77 from battery 1'53, and through the tuned intermediate circuit 179, 180, 181 and 180" the impulses produce an alternating E. M. F. in coil 183 which is transmitted by way of leads 8% and 18 1. Resistance 18 serves to dctc-i inc the intensity and decrement of: the oscillations pro duced'. When hey 1'25 deyn'essed, alternating'E'. M. F. of opposite phase is produced at terminals 184i and 18 1', thus providii tor the production of dashes, whilst the deprcs sion of key 175 produce-s dots. The system thus described is complete in itself, producing alternating current of a steady frequency, determined by the rate 01 vibration o l the reed, without requiring an alternating current generator of the rotating type.

A particular advantage of a system 03' l ype when used in connection with combined alternating and direct current signaling systems resides in the fact that by virtue of tuned circuit 179, 180', 180" and 181 being nductively associated with the genera-t. 1 7 source and output circuitthe rination of alternatin current signals is e ected w out the production of transient uni-directional current impulses which would tend to disturb direct current receiving apparatus at the remote end the transmission system.

If it be desired to use an alternator, as shown in Figure 6, to prod ce thesigna a current for cable code no" mg, then it is desirable to govern its speed so as to keep it running in synchronism (or a multiple thereof) with a vibrating reed, because of the constancy of frequency of the latter. Figure 12 shows a form of governor adapted to do this. At 187 is the armature of a direct current motor, driving the shaft 186 to which is connected the signaling alternator whose speed is to be controlled. At 188 is the motor field, excited by source 189 through series resistances 190 and 190, and itis by means of the resistance 190 that the controlling effort 011 the motor speed is exerted. A shaft 192, either the motor shaft itself or gear-driven thereby if necessary, carries a drum coniprised of two metal members 193 and 194, configured as crown gear wheels with pointed teeth, the teeth of the two members being forced tightly together but insulated from each other by pressed mica insulation, or the like. This drum rotates with shaft 192, and on its periphery has bearing against it a sliding contact or brush 201 arranged to traverse across the face of the drum, parallel to the shaft, by means of a pivot joint 200. Brush 202 establishes electrical contact with one member 194 of the drum, whilst member 193 is completely insulated. Brushes 201 and 202 are connected by leads 204 and 203, respectively, across resistance 190, and by rotation of the drum 193-194;, resistance 190 is momentarily short circuited by brush 201 making contact with drum member 194. The short circuit is continuous when brush 201 rests on member 194 at the right hand end of the drum, and does not exist at all when the brush is on member 193. The effectiveness of the successive short circuits depends, therefore, on the position of the brush along the face of the drum, and thus'by changing the field excitation of the motor, the motor speed is controlled by the position of brush 201. Further mechanism is now employed to control the position of brush 201 so as to keep the motor 187 and its alternator running synchonously with the vibrating reed. At 191 is a phonic motor of usual type, driven by a vibrating reed, not shown in the figure so that its speed is steady. 191' is the shaft of the phonic motor, and it carries on its end one main gear of a differential gearing 197; the other main gear of the differential is carried by shaft 195, the latter being a prolongation of shaft 192. The two shafts and their gears run in opposite directions, and therefore any difference in their speeds is com-' municated to the ring 196 carrying the idler pinions of the differential gearing. Motion of the ring 196 of the differential is communicated by link member 198 to lever 199 to effect the motion of brush 201 along the face of the drum in such a direction as to restore equality between the speeds of shafts 195 and 191'. A spring 205 acts on lever 199 to take up any lost motion in the mechanism, and stops 206 and 207 are provided to prevent excessive motion of ring 196 and brush 201. When these stops come into play because of excessive speed differences between shafts 195 and 191, then the comparatively weak phonic motor 191 will be driven at other than its normal speed by shaft 195 acting through the differential gear, but this is of no consequence, as it does not occur in normal running. Perfectly steady running of motor 187 and its attached alternator is thusestablished, and this is an essential to cable code A. 0. working as described previously.

In practical telegraphy it is necessary to preserve a record of outgoing signals, and in cable code A. C. working this is conveniently done by driving a small commutator or rectifier contacts by the signaling alternator shaft, a portion'of the outgoing current thus being rectified and subsequently delivered to an ordinary siphon recorder to establish the desired record of the signals.

Further, it is of distinct advantage in either kind of alternating current signaling herein described (Morse or cable code) to have the transmitter forming the signals driven at a steady speed, and preferably driven in step with the alternating current source so that every signal contains exactly the same number of alternating current cycles (or multiples thereof when Morse code dashes or block cable code signals are involved). A convenient way to attain this synchronous running of transmitter and alternator is shown in Figure 13. At 208 is the alternator armature supplying signals over leads 209. The shaft 208 of the alternator carries a cam 210 operating contact levers 212 and 212 on electric contacts 211 and 211 respectively. These contacts then produce impulse currents from battery 215 and lead 214 through leads 213 and 213 respectively to operate a usual type of phonic motor 216. This phonic motor acts through gearing 217 to drive the automatic transmitter 218, controlling, as described in Figure 6, the delivery of current from battery 219 to alternator field 220 for the formation of signals. By suit-ably choosing the gearing 217, any desired number of alternator cycles can thus be used in each signal element. If a generating system as shown in Figure 11 is employed, then the phonic motor can be driven from auxiliary contacts operated by the vibrating reed in the usual manner, and the desired relation between the alternating current cycles and the formation ofsignals at the transmitter thus secured.

WVliilst it will. be understood from the foregoing description and appended claims that the invention is in no way limited in application to systems using cable code signals it is to be noted that this invention makes it possible for cable code signals to be utilized in alternating current signaling systems, certain practical embodiments being described and illustrated herein. This constitutes an important departure in the art and particularly in submarine cable te-legraphy utilizing multiplex systems.

I claim:

1,. In alternating current signaling systems utilizing a signal code composed o't different types ot signal elements constituted by currents oi diii'ercnt phase, means for producing change of phase in the alternating current, signals constituted by such current,

said s 'nais applied to receiving apparatus and said apparatus incorporating means tor connnutating the received current.

2. In alternating current signaling; systems utilizing a signal code composed oi different types of si 'nal elements constituted by currents of diiierent phase, means for producing change of phase in the alternating current, signals constituted by such current, apparatus for receiving said signals, and means carried by said apparatus for reversing each current alternation near the zero instant in every half cycle.

3. In alternating current signaling sys tems, means for producing change of phase in the alternating current, signals constituted by said current, said signals applied to receiving, apparatus and said apparatus incorporating means for commutating each current alternation near the peak values thereot.

i. In alternating current signaling systems means for producing change of phase in the alternating current, signals constituted by said current, said signals applied to receiving apparatus, said apparatus incorporating means for connnutating each current alternation near the peak value thereof, the currents resultant upon said commutation applied to synchronizing apparatus and said apparatus establishing commutation nearly as possible at said peak values.

5. In alternating current signaling systems means for producing change of phase in the alternating current, signals constituted by such current, said signals applied to receiving apparatus, said a pparatus incorporating means for connnuta mg each alternation near the peak values thereof, synchro nizing apparatus for establishing commutation as nearly as possible at said peak values, and the angle of departure of commutation from such values determining the resultant corrective current applied to said synchronizing apparatus.

6. In alternating current signaling systems, means for changing the phase of ti o alternating current, signals constituted by said current, said signals applied to receiving apparatus, said apparatus incorporating means for eli'ecting phase reversals near each zero instant of each received current alterna tion and means for commutating said alternations near the peak values thereofla corrective current produced by departure of commutation from the peak values, said latter current applied ,to synchronizing apparatus and said latte-r apparatus maintaining s nchronism between the apparatus for effecting current reversals at each zero instant and such ins ants in the incoming signals.

7. In alternating current signaling systems, means for producing change of phase in the alternatin current, signals constituted by said current, said signals applied to receiving apparatus, two coimnutators associated with said apparatus, said commutators arranged in time phase quadrature, one of said commutators commutating the received current near the peak values thereof and the other of said commutators commutating said current near the zero values thereofi 8. In alternating current signaling systems, signals constituted by the alternating current, said signals in part distinguished from one another by change of phase in said current, said signals composed of two types of elements and applied to receivin apparatus, means associated with said apparatus for commutating the received current near the peak values thereof, two corrective currents produced consequent upon departure of commutation from said values, the corrective currents produced by one type of element being in a direction opposite to the corrective currents produced by the other type of element, means for constituting one unidirectional current from said corrective currents and means for applying such unidirectional current to synchronizing apparatus for establishing and maintaining synchronism at said peak value.

9. In alternating current signaling systems, signals constituted by the alternating current, said signals composed of a plurality of different types of elements, means for producing change or phase in said current at pro-determined intervals in the formation of said signals, receiving apparatus to Which the signals are applied, means associated With said apparatus for commutating the received alternations near the peak values thereof, corrective currents producedconsequent upon departure of commutation from said peak values, the direction of the corrective current at any instant dependent upon'the type of element received, all of the corrective currents applied to a relay, said relay functioning to combine all of said corrective currents into one uni-directional current, said latter current applied to synchronizing apparatus and said apparatus maintaining communtation as nearly as possible at said peak values.

10. In alternating current signaling systems, signals constituted by the alternating current, means for producing phase reversal of said current at one end of each successive signal, said signals applied to receiving apparatus, said apparatus incorporating a polarized relay, the incoming signals applied to the coil thereof, antennae carried by said coil said antennae co-acting with butts to energize a second relay coil and said latter relay operating recording apparatus.

11. In alternating current signaling systems signals constituted by the alternating current, said signals composed of two elements, said elements in part distinguished from one another by phase reversal of said current, said signals applied to receiving apparatus said apparatus incorporating two commutators in time phase quadrature, one of said commutators commutating the received current near the zero values of the alternations thereof, the output of said commutator applied to two relays, one of said relays recording the signals, the other of said relays en ergizing one coil of a double coil relay, the other coil of said latter relay energized from the commutator commutating the signals near the peak values of the alternations thereof, departure of commutation from the peak and zero values producing unbalanced currents in said two coil relay, such latter currents producing deflection of the relay coil and deflection of said coil actuating synchronizing apparatus to establish and maintain. commutation as nearly as possible at said peak and Zero values.

12. In alternating current signaling systems as claimed in claim 11 deflection of said two coil relay operating one of two contacts, each of said contacts operating relays, said relays varying the period of vibration of a viln-ating reed, said reed operating a phonic motor and said motor driving the commutators.

13. In alternating current signaling systems as claimed in claim 11, a pair of contacts adapted to be operated by the deflection of said two-coil relay, said contacts closin the circuit of an electric motor, operation 0 one contact producing rotation of the motor in one direction and operation of the other contact producing rotation of the motor in the opposite direction, said motor driving a train of differential gearing and said gearing interposed between the phonic motor and the commutator-s whereby operation of said gearing varies the phase of the commutators relative to that of the phonic motor.

14. In alternating current signaling systems, signals constituted by the alternating current, means for producing phase reversals in said current, said signals applied to a relay, deflection ofsaid relay effected by the signals in, one of two directions dependent upon the type of signal element received at any instant, a second relay operated by the first relay for recording the signals, a reversing switch, said switch applying the alternating signal currents in phase to a correcting relay, the field of said latter relay energized from a local alternating current source, lack of synchronism between said source and the signal currents producing deflection of said correcting relay and said deflection applying a corrective efifort to establish synchronism.

15. In a telegraph signaling system, a direct current signaling system in combination with an alternating current signaling system and means for producing change of phase in the alternating signal current.

FREDERICK EUGENE PERNOT. 

